1. Field of the Invention
The present invention relates to an image processing integrated circuit (large-scale semiconductor integrated circuit) used in a personal computer and the like and to an image processing method.
2. Description of the Related Art
As shown in FIG. 1, a conventional image processing integrated circuit 110 mainly includes a central processing unit (CPU) 101, a random access memory (RAM) 105 and a digital-analog (DA) converter 107.
The CPU 101 supplies a digital image data (D1) of one frame to the RAM 105. The term “one frame” means one screen displayed in a display 109. The RAM 105 stores the image data (D1) of one frame therein in accordance with a write destination address (A) supplied from the CPU 101.
The RAM 105 has a plurality of memory cells, each of which is constituted by addresses and bits. The addresses and bits of the memory cell correspond to display positions and display states of the display 109, one to one.
The DA converter 107 supplies a read destination address (B) to the RAM 105, receives a digital image data (D2) corresponding to the read destination address (B) from the RAM 105 and then converts the digital image data into analog image data. Moreover, each time a digital-analog conversion of the image data is completed, the DA converter 107 supplies a read destination address (B) of a next memory cell to the RAM 105. Here, the write destination address (A) and the read destination address (B) correspond one to one. The display 109 displays the analog image data supplied from the DA converter 107 at each specified pixel position.
As described above, when the digital-analog conversion of the image data for one frame is finished, the CPU 101 supplies a digital image data (D1) for the next frame to the RAM 105. Image processing is performed by repeating the above operation.
Next, description will be made of a defect position in the display 109 when there is a defect in the RAM 105, using FIG. 2. To simplify the description, herein, an image data composed of 8 bits (bits of 0 to 7) corresponds to each address of the RAM 105, and the image data shows brightness for one pixel of the display 109. Moreover, it is assumed that a write destination address 1 corresponds to a pixel at an upper left corner of the display 109 and a write destination address 2 corresponds to a pixel next to the foregoing pixel on its right. Herein, the next write destination address of a rightmost pixel of the display 109 moves to a leftmost pixel in the following line, and write destination address 99999 represents a pixel at the lower right corner of the display 109.
As shown in FIGS. 2A to 2C, it is assumed that a defect occurs, in which bits 6 and 7 of the address (write destination address; read destination address) 3 of the RAM 105 are fixed to 0. When the bit 7 is the most significant bit upon the digital-analog conversion, the brightness of these high two bits is altered remarkably. In other words, when the both bits become 0, a pixel is displayed in a near-black color at a display position of the display 109, the display position corresponding to the address (write destination address; read destination address) 3. Since the addresses of the RAM 105 and the display positions of the display 109 correspond one to one, as shown in FIGS. 2A to 2C, the display position of the display 109, which corresponds to the address 3, is displayed in a near-black color throughout a first frame, a second frame and a third frame.
For example, in the case where image data for 100 frames is stored/read to the RAM 105 per second, since the write destination addresses (read destination addresses) of the RAM 105 and the display positions of the display 109 remain unchanged during the 100 frames, the near-black color is displayed at the same display position. Consequently, a person's eyes looking at the display 109 perceive black dots, and thus the person is disturbed by the defects.
Note that, when a defect occurs, in which the bits 6 and 7 of the address (write destination address; read destination address) 3 of the RAM 105 are fixed to 1, the display 109 displays a near-white color. Similarly, a person's eyes looking at the display 109 perceive white dots, and thus the person is disturbed by the defects.